In general, in an automotive headlamp using LEDs (light-emitting diodes), it is beneficial to manage the heat dissipated by the drive circuitry and by the LEDs themselves. Heat management approaches using large heat sinks or actively driven cooling fans are known, but these such components add weight, cost, restrict design space, and in the case of an actively driven fan can decrease overall robustness of the system. Software approaches to heat management are known such as programming the drive circuits to decrease power to lower the heat generated when temperature exceeding a pre-determined threshold is sensed, but this is also expensive.
The following vehicle lamps are known: U.S. Pat. No. 7,329,033 (Glovatsky); U.S. Pat. No. 6,497,507 (Weber); U.S. Pat. No. 6,447,151 (Jones); U.S. Pat. No. 7,478,932 (Chinniah); U.S. Pat. No. 6,676,283 (Ozawa); U.S. Pat. No. 6,595,672 (Yamaguchi); U.S. Pat. No. 6,071,000 (Rapp); U.S. Pat. No. 6,021,954 (Kalwa); U.S. Pat. No. 5,406,467 (Hashemi); and Application US 2011/0310631 (Davis). In U.S. Pat. No. 7,329,033 (Glovatsky) it is known to provide cooling air to ducts arranged in a headlamp assembly using a forced convective flow shown in FIG. 2A therein which occurs as the vehicle is moving forward; or a natural convective flow shown in FIG. 2B therein; or by use of an additional fan as forced air flow shown in FIGS. 2C-D therein. U.S. Pat. No. 6,021,954 (Kalwa) discloses a headlamp housing whose interior space is aerated by regulating a valve responsive to humidity.